Method and apparatus for on-demand stencil chemical etch direct parts marking automation and carrier for chemical etch stencil mesh

ABSTRACT

A unit for on-demand chemical etch. Stencil media is unwound from a stencil unwind hub and passed underneath the thermal print head and printed. The stencil media is a sandwich that is comprised of a porous material married to a pressure-sensitive adhesive coated carrier to supply stiffness and support to the mesh. After the stencil is printed, the carrier is peeled away and is rewound onto a carrier rewind hub, leaving only the printed stencil. This printed stencil is transported underneath the etching electrode, at which time, the electrode actuates downward, sandwiching the printed stencil between the electrode and the target object so that the chemical etching process may be performed. The spent stencil rewinds onto a stencil rewind hub. The stencil printing and etch functions can be provided in a handheld unit. The handheld unit is comprised of an actuating etching head, a print head, a ribbon support system and media support system.

[0001] This application claims the benefit of U.S. ProvisionalApplication 60/420,023, filed Oct. 21, 2002 entitled Method AndApparatus For On-Demand Stencil Chemical Etch Direct Parts MarkingAutomation And Carrier For Chemical Etch Stencil Mesh

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a method for automatic on-demandchemical etching.

[0004] 2. Description Of Related Art

[0005] Electro-chemical etching uses an electric charge to remove and/ordiscolor a conductive metal surface. This process uses several items: apower source, etching solution, stencil mask, applicator, and groundelectrode. The electrolysis is limited to an area defined by a reverseimage on the stencil mask through which the metal surface is oxidized orrusted creating the desired mark.

[0006] At this time, the serialization of parts using direct partmarking technologies (laser, dot peen, chemical etch) is not feasibledue to the combination of cost and short cycle times. For example, thelaser solution is fast, but requires a large capital investment.Chemical etch on the other hand is cheap, but prior to the presentinvention could not be automated in conjunction with serialization.Manual automated chemical etching processes exist that imprint identicalinformation on many items in an assembly line fashion, for example,marking “Rotation” on a table-saw blade, i.e. the exact same mark on allthe blades being manufactured. However, these automated units can onlyprovide marks that have static information, i.e. they reapply the samestencil again and again. There is a need for a method for chemical etchin those applications that require on-demand automation.

[0007] The prior art chemical etch processes are predominately conductedat tabletop locations as both laser and dot-peen marking systemsrequired a fixed location in order to maintain process control.

SUMMARY OF THE INVENTION

[0008] A device for automatic on-demand chemical etching. Stencil mediais unwound from a stencil unwind hub and passed underneath the thermalprint head and printed using thermal transfer ribbon. The stencil mediais a sandwich that is comprised of a porous material (mesh) married to apressure-sensitive adhesive coated carrier to supply stiffness andsupport to the mesh. The thermal transfer ribbon is unwound from aribbon unwind hub and rewinds onto a ribbon rewind hub.

[0009] After the stencil is printed, the pressure-sensitive adhesivecoated carrier is peeled away and is rewound onto a carrier rewind hub,leaving only the printed stencil. This printed stencil is transportedunderneath the etching electrode, at which time, the electrode actuatesdownward, sandwiching the printed stencil between the electrode and thetarget object so that the chemical etching process may be performed. Thespent stencil rewinds onto a stencil rewind hub.

[0010] The stencil printing and etching functions can be incorporatedinto a handheld unit. The handheld unit is comprised of an actuatingetching electrode “head”, a print head, a ribbon support system andmedia support system. The thermal transfer ribbon (TTR) is used to printthe desired image onto the media. After being printed, the carrier isremoved from the printed stencil and rewound on the carrier rewind hub.The stencil is then conveyed underneath the actuating electrode “head”.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is the mesh with cover line.

[0012]FIG. 2 is an embodiment of the invention in a production line.

[0013]FIG. 3 is an alternative embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0014] An on-demand printed stencil mask is created using a thermaltransfer printer and ribbon as described in applicant's prior U.S.application Ser. No. 09/961,740 filed Sep. 4, 2001, now ______ is herebyincorporated by reference. A desired image is printed onto a carrierweb/mesh surface 2 in a reverse, inverse format. The ribbon ink acts asan insulator for the etching solution.

[0015] The stencil mesh 4 used to create a mask for the mark/image is awoven mesh fabric 4 that has very low stiffness properties. Alone, themesh 4 is difficult to reliably feed through a thermal printer.Laminating a carrier liner 8 to the backside of the mesh 4 allows thematerial to feed through a thermal printer and cutter while printing amask stencil pattern of the surface.

[0016] The mesh 4 consists of a finely woven polyester filamentlaminated to a carrier liner 8. The carrier provides the necessarystiffness to properly track and feed the mesh through a thermal printerand cutter mechanism. The carrier liner 8 is held to the backside of themesh material 4 with a light removable pressure sensitive adhesive 6.

[0017] The carrier 8 may be a paper or film substrate in the range of0.0005″ to 0.020″ thick. The pressure sensitive adhesive 6 is, forexample, a removable microsphere pressure sensitive adhesive 6 with acoating thickness between 0.0001″ to 0.010″ thick. The selected adhesiveis compatible with the woven mesh fabric 4 if it does not permanentlybond, flow into or otherwise block the mesh openings.

[0018] The inventive device is a unit for automatic on-demand chemicaletch. Stencil media 2 is unwound from a stencil unwind hub and passedunderneath the thermal print head 22 and printed using the ribbon 24.The stencil media 2 is a sandwich that is comprised of a porous material(mesh) 4 married to a pressure-sensitive adhesive 6 coated carrier 8 tosupply stiffness and support to the mesh 4. The thermal transfer ribbon24 is unwound from a ribbon unwind hub 14 and rewinds onto a ribbonrewind hub 16.

[0019] After the stencil is printed, the carrier 8 is peeled away and isrewound onto a carrier rewind hub 18, leaving only the printed stencil.This printed stencil is transported underneath the etching head 20, atwhich time, the electrode of the etching head actuates downward,sandwiching the printed stencil between the electrode and the targetobject 30 so that the chemical etching process may be performed. Thespent stencil rewinds onto a stencil rewind hub 12.

[0020] By maintaining the continuous nature of the webs, the process maybe automated and controlled through a computer that will control themovement of the target part as well as the etching process. As eachtarget object arrives at the etching station data associated with thatobject has already been printed to a mesh stencil for etching theobject.

[0021] In a second embodiment, an etching unit would etch objects on theconveyor 28 using pre-printed stencil(s). The printing mechanism wouldbe eliminated and the stencils would be loaded into the etching unit andconsumed one at a time. This would provide a means of etching theinformation in a location where the data used in each mark is knownbeforehand but the printer communication with the host is difficult orunfeasible, for example in a remote warehouse.

[0022] In a third embodiment, the conveyor 28 is modified. The etchingprocess requires a grounding electrode to operate. Rather than have agrounding electrode on the etching head mechanism, this embodiment usesthe conveyor 28 as the grounding point. Also, rather than have theetching unit actuate down to the item being etched, the conveyor 28itself may be actuated upwards to push the object 30 being markedagainst the etching head 20.

[0023] As shown in FIG. 3, the required media paths, previouslydescribed with respect to FIG. 2, may be incorporated into a handheldunit. A fourth, fifth, sixth and seventh embodiment describes equipmentand a process that can produce etched marks in a mobile environment.These embodiments describe a way of reducing the chemical etch processto a mobile handheld unit 30 that can be used with complete freedom ofmovement. The mobile hand-held units would be useful for direct markingin situations that do not lend themselves to a fixed location (i.e.inspections serialization, recalls, process overflow, etc.).

[0024] A fourth embodiment combines the stencil printing and electrodefunctions into a handheld unit 30. The handheld unit 30 is comprised ofan actuating etching head 20 with an electrode, a print head 22, aribbon support system 14, 16 and media support system 10, 12, 18. Thethermal transfer ribbon 24 is used to print the desired image onto themedia 2. After being printed, the carrier 8 is removed from the printedstencil and rewound on the carrier rewind hub 18. The stencil is thenconveyed underneath the actuating electrode head 20. Once in thisposition, the electrode extends, sandwiching the stencil between theelectrode 20 and the target object 32 surface. The electrode is thenenergized and the desired mark produced.

[0025] A fifth embodiment consists of a hand-held unit 30 that does nothave a printing unit contained within it. Pre-printed stencils areloaded into the unit and are used in much the same way as with thefourth embodiment. This embodiment has the advantage of being asimplified system that is more economical to manufacture and maintain.

[0026] A sixth embodiment would consist of a hand-held unit 30 that usesstencils delivered in a stacked cartridge format. The stencils areloaded into a cartridge, as a stack of pre-printed stencils. Thesestencils would then be fed individually to the etching head 20,consumed, and then conveyed either out of the unit or into a collectionbin (part of the hand-held unit). This would also provide another way ofetching using non-roll-form stencil constructions (i.e. stencils madeusing photographic methods).

[0027] A seventh embodiment would consist of a hand-held unit employinga replaceable etching head that is spherical in shape and would employseveral fixed stencils (similar to a Daisy-wheel typewriter head). Thisunit would provide a means of etching a fixed message to an asset suchas “Rejected”, “Quality”, etc. To change the group of messages availablefor etching, the etching head would be exchanged.

[0028] Each of the above embodiments could also be constructed using anon-actuated, fixed position head 20 that would protrude from the frontface of the unit enough for the head to contact the target surface inorder to perform an etch. Also, the hand-held etching unit 30 can beeither plugged in and used, or be incorporated into a mobile system thatconsists of the hand-held etching unit, a mobile power source and ifdesired for the type of part to be marked, a work area to support thepart.

[0029] In each of the embodiments, the etching solution is applied priorto activation of the electrode to wet the metal surface to be marked.Etching solution delivery may be via a brush/sponge or applied in a dripfashion to a pad on the electrode which is continuously supplied with anetching solution supply, similar, for example, to a gravity fed oiler.

[0030] Wetting of the electrode head with the etching solution may alsobe accomplished, for example, via a separate applicator or sponge. Ifthe etching solution is corrosive a part surface wiper 26 may beutilized to remove excess solution from the object after the etchingprocess is complete.

1. An apparatus for on-demand chemical etch comprising: a stencil web; amedia support system; and an etching head mechanism wherein said stencilweb transported under said etching head mechanism by said media supportsystem.
 2. The apparatus of claim 1 wherein said media support systemcomprises a stencil unwind hub and a stencil rewind hub.
 3. Theapparatus of claim 1 further comprising: a printing mechanism, saidprinting mechanism comprising a print head, a thermal transfer ribbonand a ribbon support system; and a spent carrier rewind; wherein saidprinting mechanism is located before the etching head mechanism.
 4. Theapparatus of claim 1 wherein said etching head mechanism extends andsandwiches said stencil web between said etching head mechanism and atarget object.
 5. The apparatus of claim 4 further comprising agrounding electrode on said etching head mechanism.
 6. The apparatus ofclaim 4 wherein said target object is on a conveyor and said conveyor isadapted to be actuated upwards to push the target object against theetching head.
 7. The apparatus of claim 1 wherein said stencil web ispreprinted.
 8. The apparatus of claim 1 further comprising a partsurface wiper.
 9. The apparatus of claim 1 further comprising a handheldunit wherein said stencil web, media support system and said etchinghead mechanism are adapted to be housed in said handheld unit.
 10. Theapparatus of claim 2 further comprising a handheld unit wherein saidstencil web, media support system and said etching head mechanism areadapted to be housed in said handheld unit.
 11. The apparatus of claim 3further comprising a handheld unit wherein said stencil web, mediasupport system and said etching head mechanism are adapted to be housedin said handheld unit.
 12. The apparatus of claim 4 further comprising ahandheld unit wherein said stencil web, media support system and saidetching head mechanism are adapted to be housed in said handheld unit.13. The apparatus of claim 12 further comprising a grounding electrodeon said etching head mechanism.
 14. The apparatus of claim 9 whereinsaid media support system comprises a cartridge and the stencil web isloaded in the cartridge as a stack of preprinted stencils.
 15. Theapparatus of claim 14 wherein the media support system further comprisesa collection bin adapted to hold used stencils.
 16. The apparatus ofclaim 9 wherein the etching head is spherical and comprises with aplurality of stencils.
 17. The apparatus of claim 10 wherein the etchinghead is replaceable.
 18. A method for on-demand chemical etch comprisingthe steps of: obtaining a stencil web; said stencil web on a mediasupport system comprising a media unwind hub and a stencil rewind hub;transporting said stencil web under a print head; printing in reverse onsaid stencil web to create a stencil; peeling away a carrier from saidstencil; transporting said stencil under an etching head; sandwichingsaid stencil between said etching head and an object; applying a wettingsolution; actuating an electrode; rewinding a spent stencil on thestencil rewind hub.